Microorganisms colonize dental units and contaminate dental treatment water. The formation of biofilm on water-bearing surfaces in dental units results in fouling of the water that passes through the unit with high levels of suspended bacteria. In 1993 the Centers for Disease Control and Prevention (CDC) recommended infection control practices for dentistry. The recommendations included flushing waterlines daily for several minutes and for 20 to 30 seconds between patients. The 1996 American Dental Association (ADA) statement on dental unit waterlines (DUWL) challenged the dental manufacturing industry to develop methods to control biofilm in dental unit water systems. The statement established a goal for dental water to contain no more than 200 CFU/ml (colony forming units per milliliter) of heterotrophic bacteria. The Organization for Safety and Asepsis Procedures (OSAP) issued a statement in 1996 supporting both the CDC and ADA guidelines, but containing more explicit guidance on waterline monitoring and the use of sterile irrigants in surgery. It was reported in the Journal of American Dental Association (JADA) in October of 2000 that heterotrophic bacteria counts ranging between 10,000 and 100,000 CFU/ml may be commonplace. The Safe Drinking Water Act establishes a 500 CFU/ml standard for non-coliform bacteria in drinking water.
Current approaches to improve the quality of dental water include waterline flushing, independent reservoirs filled with distilled water, chemical “shock treatment,” continuous chemical treatment, mechanical filtration and automated in-line treatment devices. Waterline flushing may temporarily reduce bacteria levels, however the biofilm remains completely active, and at any given time a patient may be exposed to elevated levels of bacteria. Independent water reservoirs filled with distilled water may begin free of bacteria, however without a residual disinfectant the water is readily contaminated from the biofilm within the DUWL.
Mechanical filtration may be temporarily effective at filtering bacteria, however problems with breakthrough, time and costs of replacement are prohibitive. In dentistry, “shock treatments” utilizing solutions with bleach, peroxide, or chlorhexidine have been administered, but the “shock treatments” must be repeated (e.g., every day) because the biofilm begins to regrow in that period of time. This type of system also requires use of only sterile water to slow down the biofilm formation. Mature biofilms are notoriously resistant to chemical disinfection including these “shock treatments.” Thus, if a practitioner does not treat his system for several weeks, the biofilm will become resistant to this method. Most biocidal agents have not been shown to destroy a mature biofilm.
U.S. Pat. No. 5,158,454 to Viebahn, incorporates an automated in-line ozone generator that is effective at continuous disinfection. This device and others similar to it are bulky, taking up limited space from the operatory unit and are expensive to install and operate.
Another system desired to control the presence of infectious microbes in water supplied to dental units is disclosed in U.S. Pat. No. 5,230,624 to Wolf et al. Here, an in-line filter is provided in a supply line leading to a dental instrument, such as a drill or the like, and contains a polyiodide purification resin. The resin functions to neutralize and kill bacteria by the release of iodine from the resin surface to the bacteria through a demand release process involving electrostatic attraction. The resin is positively charged such that the negatively charged microorganisms are attracted to the resin to the point where iodine is released directly into the microorganism. The use of iodine to treat the water may cause the water to have a foul odor and/or taste.
Another system for controlling the presence of infectious microbes in water supplied to dental units is disclosed in U.S. Pat. No. 5,709,546 to Waggoner. The system disclosed in U.S. Pat. No. 5,709,546 provides a process by which mature biofilms, including biofilms of the type produced by gram negative bacteria such as Pseudomonas aeruginosa, are reduced to the point of elimination through the use of a hydroxycarboxylic acid in relatively low concentrations so as not to be harmful to human tissue. This invention requires strict metering control of the acid and any malfunctions can result in harmful conditions to human tissue.
Therefore, a need exists for a dental water treatment agent that is bactericidal but not toxic or irritating to humans. The treated water should not have an unpleasant taste or odor. The system should detach biofilm and discourage subsequent reformation, while protecting the dental unit's internal components from corrosion or degradation. If delivered continuously in treatment water, the system should not have any effect on enamel or dentin bonding agents.